Inclusion of extruded grass pea, Lathyrus sativus seed meal in compound diets for rohu, Labeo rohita (Hamilton, 1822) fingerlings

Background. Grass pea, Lathyrus sativus is a widely available grain legume that contains a variety of anti-nutritional factors (ANFs). The aim of the present study was to determine the effects of feeding rohu, Labeo rohita, fingerlings with diets containing raw or extruded grass pea seed meal on growth, feed utilization efficiency, and carcass composition. Materials and methods. Extrusion of finely ground grass pea seeds was performed in a twin-screw extruder at 130oC and 400 rpm. Six isonitrogenous (35% crude protein approximately) and isocaloric (16 547.7 J ּ g-1) diets were formulated incorporating raw and extruded grass pea seed meal at 20, 30, and 40% levels by weight into a fish meal based control diet. The diets were fed to rohu fingerlings in triplicate treatments at the rate of 3% of body weight for 60 days and fish performance in terms of growth, apparent protein digestibility (APD), and carcass composition was studied. Results. Extrusion of grass pea seed meal was effective in significantly reducing the ANFs, such as tannins (77%), trypsin inhibitor (below detection limit), and β-ODAP (46.09%). Phytic acid and nutrient components were not affected by extrusion. In terms of growth response, FCR and PER, 40% extruded grass pea meal incorporated diet resulted in significantly (P < 0.05) the best performance of rohu fingerlings. The APD values obtained for extruded seed meal incorporated diets were significantly higher in comparison to those for non-extruded ones. The carcass protein and lipid contents increased over the initial value in all dietary treatments with no significant differences in fish fed diets containing extruded grass pea seed meal. Conclusion. Extrusion is an effective treatment to reduce/eliminate the ANFs in legumes. Improved growth, feed utilization efficiencies, and APD in rohu fingerlings indicate that extrusion processing is also effective in improving the nutritional characteristics of grass pea.